Such a device has in general a torque input element, a torque output element, and elastic members mounted between the torque input and output elements and counteracting rotation of one of said elements with respect to the other.
When the torque transmission device is of the long travel damper (LTD) type, it comprises several groups of elastic members in which the elastic members of a single group are arranged serially by means of a phasing member so that the elastic members of each group deform in phase with one another.
The document US 2010/0269497 describes a hydraulic torque converter intended to couple an output shaft of an internal combustion engine, such as a crankshaft, to an input shaft of a gearbox.
The torque converter conventionally has a bladed impeller wheel capable of hydrokinetically driving a bladed turbine wheel via a reactor.
The impeller wheel is rotationally coupled to the crankshaft, and the turbine wheel is rotationally coupled to two guide washers. The latter are mounted movably around a central hub rotationally coupled externally to an annular web and intended to be coupled internally to the input shaft of the gearbox.
A clutch allows a torque to be transmitted from the crankshaft to the guide washers with no involvement by the impeller wheel and turbine wheel. This clutch has an input element coupled to the crankshaft and an output element, in the form of a splined hub, fastened to the guide washers.
Elastic members are mounted circumferentially between the annular web and the guide washers. These elastic members are grouped in pairs, the elastic members of a single pair being arranged serially by means of a common phasing member, so that the elastic members deform in phase with one another. The elastic members exhibit substantially the same stiffness constant.
Pendular damping means are mounted on the phasing member and have pendular masses fastened movably on the radially outer periphery of the phasing member.
The pendular damping means and the elastic members allow vibrations and rotational irregularities, due especially to the explosions of the internal combustion engine, to be absorbed and damped.
Pendular damping means of this kind can be used on other torque transmission devices, in particular such as dual mass flywheels.
It is known that a dual mass flywheel conventionally has a primary flywheel intended to be coupled to a crankshaft, and a secondary flywheel intended to be coupled to an input shaft of a gearbox by means of a clutch.
The two flywheels are rotationally movable with respect to one another, and are coupled in particular by means of elastic members. The stiffness constants of the elastic members are substantially identical to one another.
Pendular masses can be mounted on a support constituted by a movable element of the dual mass flywheel, for example a guide washer, an annular web, or a phasing member.
The masses are then mounted on the support, generally by means of guide rollers engaged into oblong circular-arc holes of the masses and of the support. The concavities of the mass holes are opposite the concavities of the support holes. The resulting motion of the masses is pendular, and depends on the shape of the oblong holes.
In operation, during rotation of the movable support on which the masses are mounted, the latter become displaced between two extreme positions.
In these torque transmission devices it has been found that the phasing members generally have a relatively low resonant frequency or natural frequency, so that they generate vibrations for engine speeds between, for example, 1000 and 1500 rpm; these vibrations can cause noise or can have a negative impact on the comfort of vehicle users.